title: Resolution behavior of cis- and trans-octadecenoic acid isomers by AOCS official method using SP-2560 column.
abstract: The gas chromatography-flame ionization detector equipped with a higher polarity column (i.e., SP-2560) has often been used for the quantification of trans-fatty acids in food. In particular, AOCS Ce 1h-05, the official method of the American Oil Chemists' Society (AOCS), is a highly effective method to separate the isomers of trans-fatty acids. In this study, the resolution behavior and the response factors of cis- and trans-octadecenoic acid methyl ester (C18:1-ME) isomers separated by the AOCS Ce 1h-05 method were investigated, and the contents of each cis- and trans-C18:1-ME isomer in partially hydrogenated vegetable oil (PHVO) and milk fat were quantified by using the calibration curves obtained for the respective isomers. The relative response factors for the trans- and cis-C18:1-ME isomers against the internal standard heneicosanoic acid methyl ester (C21:0-ME) were 1.031 ± 0.040 (mean ± SD) and 0.990 ± 0.032, respectively. The relative response factors of trans-isomers tend to be higher than those of cis-C18:1-ME isomers. The peaks of cis-4-C18:1-ME, cis-5-C18:1-ME, cis-6-C18:1-ME, cis-7-C18:1-ME, cis-8-C18:1-ME, and cis-9-C18:1-ME isomers overlapped with those of trans-C18:1-ME isomers. Both PHVO and milk fat contained many types of cis- and trans-C18:1 isomers, and the total contents of the trans-C18:1 isomer in PHVO and milk fat were 28.01 g and 3.62 g per 100 g oil, respectively. When the trans-C18:1-ME isomer was separated from the cis-C18:1-ME by using a silver-ion cartridge column before the analyses, the total contents of the trans-C18:1 isomer in PHVO and milk fat were 23.03 g and 2.78 g per 100 g oil, respectively. The difference in the trans-C18:1 isomer content between the two methods was ascribed to the partial overlapping of cis-isomer peaks with the peaks of trans-C18:1-ME isomers, in the chromatogram.
authors.affiliation: Tsukishima Foods Industry Co. Ltd.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Yoshinaga
authors.forename: Masaharu
authors.initials: M
authors.lastname: Asanuma
authors.forename: Chao
authors.initials: C
authors.lastname: Xu
authors.forename: Hoyo
authors.initials: H
authors.lastname: Mizobe
authors.forename: Koichi
authors.initials: K
authors.lastname: Kojima
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Nagai
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Beppu
authors.forename: Naohiro
authors.initials: N
authors.lastname: Gotoh
mesh_terms: D000818:Animals; D002849:Chromatography, Gas / Q000295:instrumentation / Q000379:methods*; D005504:Food Analysis / Q000379:methods*; D007536:Isomerism; D008892:Milk / Q000737:chemistry*; D010938:Plant Oils / Q000737:chemistry*; D013229:Stearic Acids / Q000032:analysis* / Q000302:isolation & purification; D044242:Trans Fatty Acids
chemical_list: C114874:5-octadecenoic acid; D010938:Plant Oils; D013229:Stearic Acids; D044242:Trans Fatty Acids